Method and installation for the indirect reduction of particulate oxide-containing ores

ABSTRACT

In a process for the gas reduction of particulate oxide-containing ores, in particular iron-oxide-containing material, in the fluidized-bed process at a pressure of &lt;5 bars, wherein the ore by aid of a reducing gas produced from coal is heated, optionally also pre-reduced, in a fluidized-bed reactor ( 1 ) designed as a pre-heating stage ( 5 ), subsequently is reduced to sponge iron in at least one fluidized-bed reactor ( 2, 3 ) designed as a reduction stage ( 7, 8 ), the reducing gas via a reducing-gas feed duct ( 12 ) or reducing-gas duct ( 13 ) being conducted from the reduction stage ( 7, 8 ) to the pre-heating stage ( 5 ) in the opposite direction of the material to be reduced and conducted from stage to stage, and being drawn off as an export gas after purification, heat is supplied to the reducing gas fed to the reduction stage ( 7, 8 ) and/or pre-heating stage ( 5 ), namely by combustion, together with oxygen and/or air, of a portion of the reducing gas provided for the gas reduction in the reduction stage ( 7, 8 ) and/or the pre-heating stage ( 5 ). (FIG. 1)

[0001] The invention relates to a process for the gas reduction ofparticulate oxide-containing ores, in particular iron-oxide-containingmaterial, in the fluidized-bed process at a pressure of ≦5 bars, whereinthe ore by aid of a reducing gas produced from coal is heated,optionally also pre-reduced, in a fluidized-bed reactor designed as apre-heating stage, subsequently is reduced to sponge iron in at leastone fluidized-bed reactor designed as a reduction stage, the reducinggas via a reducing-gas feed duct or reducing-gas duct being conductedfrom the reduction stage to the pre-heating stage in the oppositedirection of the material to be reduced and conducted from stage tostage, and being drawn off as an export gas after purification, as wellas to a plant for carrying out the process.

[0002] In case the reduction of the particulate oxide-containing oretakes place in several fluidized-bed reactors subsequently connected,the reducing gas being conducted from one reactor to the other incounterflow to the ore, the solid gets heated up stepwise while theenthalpy of the reducing gas decreases at the same time, partly due alsoto the reactions taking their course in the reduction. This may possiblylead, in the individual reduction stages for the solid, to temperaturesthat are so low that the reaction between reducing gas andoxide-containing ore is impeded kinetically and thermodynamically, i.e.,the reduction of the ore is not done up to the desired degree during itstemporal residence in the reduction reactor.

[0003] In a process of the initially mentioned kind, known from AT 402937 B, iron-oxide-containing material is reduced in four fluidized-bedreduction zones subsequently connected in series. In order to set aconstant, more or less equally high temperature in all of thefluidized-bed reduction zones, freshly formed reducing gas is, inaddition to the reducing gas flowing through the fluidized-bed reductionzones arranged in series, in part fed directly to the fluidized-bedreduction zones following the fluidized-bed reduction zone arrangedfirst in the direction of flow of the reducing gas, so that thefluidized-bed reduction zones are connected both in series and inparallel with regard to the reducing-gas conduct. Here, the additionallyfed, freshly formed reducing gas is preferably fed to the individualfluidized-bed reduction zones in an amount of 5 to 15%.

[0004] However, a disadvantage connected therewith is that thepre-reduction stages have to be configured for gas amounts gettingbigger and bigger towards the pre-heating stage as in each stagefollowing the final reduction stage additional fresh reducing gas isadded to the reducing gas leaving the preceding stage. Supposing furtherthat in the final reduction zone a specific amount of reducing gas is inany case required for the complete reduction of the material used,irrespective of whether there is an additional parallel guidance of thereducing gas or not, an arrangement according to AT 402 937 B results,all in all, in a higher consumption of reducing gas.

[0005] In WO 97/13880 A and WO 97/13878 A there is described a processin which a portion of a reducing gas flowing from a final reductionstage into a pre-reduction stage is branched off, scrubbed, purifiedfrom CO₂ and heated and subsequently is recycled into the finalreduction stage. In the pre-heating stage, oxygen is burnt with aportion of the reducing gas introduced into this stage, for the purposeof increasing its temperature.

[0006] According to WO 97/13880 A and WO 97/13878 A, only thetemperatures in the fluidized-bed reactors corresponding to the finalreduction stage and the pre-heating stage are controlled by way of a gasrecycling and/or partial combustion. The reactors located between thesetwo stages are, however, dependent on the conditions in thefinal-reduction fluidized-bed reactor.

[0007] From JP 58-34114 A there is known a process for the reduction offine-grained iron ore, in which the reducing gas for the final reductionstage is produced by decomposition and reformation of hydrocarbon bymeans of the oxidizing off-gas drawn off the final reduction zone, theiron ore being pre-reduced in a first stage by carbon separated from thehydrocarbon. For providing the energy needed for the production of thereducing gas, the oxidizing off-gas is heated before being brought intocontact with the hydrocarbon.

[0008] In U.S. Pat. No. 3,985,547 A there is described a process for thereduction of iron ore in a multiple fluidized-bed reactor, in whichfresh reducing gas is produced by substoichiometric combustion ofmethane and oxygen in a burner associated with the reactor, which isarranged with its outlet opening between the lowermost fluidized bed andthe fluidized bed located thereabove. The spent reducing gas leaving theuppermost fluidized bed is purified, liberated from water and CO₂ and,in the heated state, fed to the lowermost fluidized bed as a recyclingreducing gas.

[0009] The invention has as its object to provide, in a process of theinitially described kind, a possibility of independent temperatureincrease in the individual reduction stages without having tosubstantially increase the amount of reducing gas or needing an enlargeddimensioning of plant elements. The aim is to set the temperature ineach individual fluidized-bed reduction stage and to set an optimumsolid/gas-temperature profile as well as gas-quality profile above thefluidized-bed stages.

[0010] According to the invention, this object is achieved in that heatis supplied to the reducing gas fed to the reduction stage and/orpre-heating stage, namely by combustion, together with oxygen and/orair, of a portion of the reducing gas provided for the gas reduction inthe reduction stage and/or the pre-heating stage. The partial combustionof the reducing gas represents the most efficient enthalpy addition andfurther offers the advantage that no substantial increase in the gasamount is necessary.

[0011] Furthermore, this object is achieved in that heat is supplied tothe reducing gas by combustion of a portion of the export gas togetherwith oxygen and/or air.

[0012] A further possibility of achieving the inventive object consistsin burning, together with oxygen and/or air, a portion of the coolinggas used for cooling the reducing gas to be introduced into the finalreduction zone, whereby heat is supplied to the reducing gas fed to thereduction stage and/or pre-heating stage.

[0013] Oxygen addition to the reducing gas allows for an individualenergy distribution to the individual reactors, so that in for examplethree fluidized-bed reactors the inlet temperature of the reducinggas-when adding oxygen/air to all three reactors-could be as follows:920° C.(1^(st) reactor)/890° C.(2^(nd) reactor)/900° C.(3^(rd) reactor).In case an oxygen/air addition was done only before the fluidized-bedreactor corresponding to the pre-heating stage (3^(rd) reactor) and thefinal reduction stage (1^(st) reactor), the inlet temperatures wouldhave to change to 920° C./750° C./1140° C. in order to obtain the samereduction result, which would lead to an increased thermal load onreactor 3 and the ore charged into reactor 3. This problem is avoided bya process according to the invention.

[0014] By an increase in the reducing-gas temperature according to theinvention, autoreforming reactions in the gas phase are preferredthermodynamically and kinetically, the dust present in the reducing gasoptionally acting as a catalyst. In these autoreforming reactions,methane is reacted with carbon dioxide and/or water vapor to becomecarbon monoxide and/or hydrogen. This in situ generation of reducingconstituents brings about an improvement of the reducing-gas analysisand thus also a thermodynamic improvement of the ore reduction.

[0015] Preferably, the portion to be burnt of the reducing gas, exportgas or cooling gas is subjected to a scrubbing operation before beingburnt, whereby locally very high temperatures originating from acombustion of dust-loaded gases and susceptible of resulting in a fusingof the dust due to a Boudouard reaction are avoided.

[0016] The oxygen and/or air necessary to the combustion of the reducinggas are fed into the reducing-gas feed duct or reducing-gas duct, whichtransports the reducing gas into the first fluidized-bed reduction zoneand/or from one fluidized-bed reduction zone into the reduction zonearranged subsequently, advantageously via lances which at the same timeact as burners. Thanks to this arrangement, the requirements as toequipment are kept very limited.

[0017] Another possibility of setting the temperature in the reductionfluidized-bed stages consists in supplying heat to the reducing gas byburning external combustible gas and/or solid and/or liquid fuelstogether with oxygen and/or air.

[0018] According to a preferred embodiment, the combustion of thecombustible gases or solid and/or liquid fuels is done in a burnerprovided in the reducing-gas feed duct or reducing-gas duct. Suitably,the duct may have an enlarged site in this area.

[0019] According to another preferred embodiment, the combustion ofcombustible gas or solid and/or liquid fuel is done in a combustionchamber separated from the reducing-gas feed duct or reducing-gas duct,the combustion gases and possibly not burnt solids subsequently beingintroduced into the reducing-gas feed duct or reducing-gas duct.Thereby, hot flame fronts that possibly appear are leveled before theyget into contact with dust-loaded reducing gas and likewise cause afusing of the dust in the ducts.

[0020] Advantageously, combustible gas or solid and/or liquid fuel isburnt together with oxygen and/or air by means of at least one burnerwhich is provided in the reduction fluidized-bed reactor. Here, thecombustion gases are introduced directly into the fluidized-bed reactor.

[0021] According to another preferred embodiment, only oxygen and/or airare fed into the fluidized-bed reactor via a burner, preferably a lance,and the reducing gas is directly burnt there.

[0022] Here, the burner suitably may be arranged either below thefluidized bed formed in the fluidized-bed reactor, on the level of thefluidized bed or above the same, whereby the heat can be supplied to thereducing gas extremely selectively and particularly efficiently.

[0023] The two latter alternatives are particularly advantageous becausehere, the thermal load on the distributor bottom is smaller and foulingof solid on and/or in nozzles or openings of the distributor bottom isprevented or at least reduced.

[0024] According to a preferred embodiment of the process according tothe invention, reducing gas and/or export gas and/or cooling gas and/orexternal combustible gas and/or solid and/or liquid and/or gaseous fuelon a hydrocarbon basis are additionally used for the combustion. Thisembodiment proves to be particularly advantageous when any fuel from theabove-indicated group is present in excess or reducing gas, export gasand/or cooling gas are needed mainly for other purposes and thereforeare not available in a sufficient quantity.

[0025] Preferably, a material increasing the proportion of reductants inthe reducing gas by at least partially reacting with the reducing gas,in particular natural gas and/or coal, is admixed to the reducing gasfed to the reduction stage and/or pre-heating stage. Hereby, thephenomenon of sticking, which impedes the reduction process, is avoided.The reason for it are directional, needle-like iron precipitations onthe surfaces of the fine ore particles, which originate at highertemperatures and a low reduction potential. The reaction of thematerials may also be done in a burner.

[0026] Feeding additional fuels allows to positively influence thetemperature setting, the oxidation degree of the reducing gas andoptionally an increase in the total gas amount.

[0027] Furthermore, the invention provides for a process in which amaterial increasing the proportion of reductants in the reducing gas byat least partially reacting with the reducing gas, in particular naturalgas and/or coal, is admixed to the reducing gas fed to the reductionstage and/or pre-heating stage, wherein no combustion takes place.

[0028] The advantages of this process are that sticking is avoided, asmentioned above.

[0029] In the following, the invention will be explained in more detailwith reference to the drawings, wherein FIGS. 1 to 3 and 9 each show anembodiment of an inventive process in a block diagram, FIGS. 4 and 5each show a preferred embodiment of the processes represented in FIGS. 2and 3, respectively, in a block diagram and FIGS. 6 to 8 show anenlarged detail of a preferred embodiment in diagrammaticrepresentation.

[0030]FIG. 1 shows three fluidized-bed reactors, 1 to 3, subsequentlyconnected in series, wherein iron-oxide-containing material, such asfine ore, via an ore feed duct 4 is fed to the first fluidized-bedreactor, 1, in which in a pre-heating stage 5 pre-heating of the fineore and, optionally, pre-reduction take place, and subsequently viaconveying ducts 6 is conducted from fluidized-bed reactor 1 tofluidized-bed reactors 2, 3. In fluidized-bed reactor 2, pre-reductionis done in a pre-reduction stage 7, and in fluidized-bed reactor 3,final reduction of the fine ore to sponge iron is performed in a finalreduction stage 8.

[0031] The completely reduced material, i.e. the sponge iron, isconducted into a melt-down gasifler 10 via a conveying duct 9. Inmelt-down gasifier 10, in a melt-down gasifying zone 11, there isproduced from coal and oxygen-containing gas a CO and H₂-containingreducing gas which via reducing-gas feed duct 12 is introduced intofluidized-bed reactor 3, arranged last in the direction of flow of thefine ore. The fluidized-bed process is carried out at a pressure of ≦5bars. In counterflow to the ore flow, the reducing gas is conducted fromfluidized-bed reactor 3 to fluidized-bed reactors 2 to 1 viareducing-gas ducts 13, via an export-gas discharge duct 14 is dischargedfrom fluidized-bed reactor 1 as an export gas and subsequently is cooledand scrubbed in a wet scrubber 15.

[0032] Melt-down gasifier 10 has a supply means 16 for solid carboncarriers, a supply means 17 for oxygen-containing gases and optionallysupply means for carbon carriers that are liquid or gaseous at roomtemperature, such as hydrocarbons, as well as for burnt fluxes. Inmelt-down gasifier 10, molten pig iron and/or molten steel pre-materialand molten slag, which are tapped via a tap 18, collect below melt-downgasifying zone 11.

[0033] In reducing-gas feed duct 12, which departs from melt-downgasifier 10 and opens into fluidized-bed reactor 3, a dedusting means19, such as a hot gas cyclone, is provided, the dust particles separatedin this cyclone being fed to melt-down gasifier 10 via recycle duct 20with nitrogen as conveying medium and via a burner 21 under blowing-inof oxygen.

[0034] From reducing-gas feed duct 12 there departs a gas recycle duct22 which via a scrubber 23 and a compressor 24 recycles a portion of thereducing gas into reducing-gas feed duct 12 again, namely before thearrangement of hot gas cyclone 19, whereby setting of the reducing-gastemperature is enabled.

[0035] In reducing-gas duct 13 or reducing-gas feed duct 12, burners 25,25′ and 25″ are each provided before fluidized-bed reactors 1 to 3 inthe direction of the gas flow, to which burners there are fed oxygenand/or air, for the partial combustion of the reducing gas, the burnersbeing formed by a feed site for combustible gas and oxygen and/or air aswell as by a combustion chamber 25 a, 25′a and 25″a. These burners 25,25′ and 25″ may also be designed as lances feeding oxygen and/or air, aportion of the reducing-gas duct acting as combustion chamber of burner25. For the purpose of feeding oxygen, also an oxygen-containing gas maybe used. By the amount of oxygen and/or air fed, the combustion and thusthe temperature of the reducing gas may be controlled individuallyaccording to the requirements of the reduction stages and/or thepre-heating stage, whereby conditions thermodynamically favorable to thereduction are created and autoreforming reactions are facilitated and,further, the thermal load per fluidized-bed reactor is reduced.

[0036] According to the process variant represented in FIG. 2, anexport-gas duct 26 branches off export-gas discharge duct 14 after wetscrubber 15, which export-gas duct via a compressor 27 feeds, in aparallel manner, a portion of the purified export gas to burners 25, 25′and 25″provided in reducing-gas ducts 13 and reducing-gas feed duct 12,so that it is burnt there together with oxygen and/or air and thusprovides the necessary heat to the reducing gas.

[0037] The inventive process represented in FIG. 3 differs from theprocess variant represented in FIG. 1 in that the supply of heat to thereducing gas is done by combustion of a portion of the cooling gastogether with oxygen and/or air and not by combustion of reducing gasfed to the fluidized-bed reactors. For this purpose, a cooling-gas duct28 branches off gas recycle duct 22 after scrubber 23, which cooling-gasduct via a compressor 29 transports in a parallel manner a portion ofthe cooling gas to burners 25, 25′ and 25″.

[0038]FIG. 4 shows a preferred embodiment of the process variantrepresented in FIG. 2. Here, export-gas duct 26 runs into burners 25,25′ and 25″, constituted by combustion chambers 25 a, 25′aand 25″a ,which burners are, in contrast with the representation in FIG. 2, notintegrated into reducing-gas ducts 13 or reducing-gas feed duct 12.

[0039]FIG. 5 illustrates that embodiment of the process represented inFIG. 3 that is analogous to FIG. 4. That portion of the cooling gas thatis destined to be burnt is burnt together with oxygen and/or air inseparate combustion chambers 25 a, 25′a and 25″a, which constituteburners 25, 25′ and 25″, and subsequently is introduced intoreducing-gas ducts 13 or reducing-gas feed duct 12.

[0040] According to a preferred embodiment of the invention, thecombustion of the combustible gas (reducing gas, export gas or coolinggas) used is done together with oxygen and/or air by means of a burnerassociated with a fluidized-bed reactor.

[0041] Fluidized-bed reactor 30, which is represented diagrammaticallyin FIG. 6, exhibits an interior space 31, divided into three zones, agas feed duct 32 leading to said interior space at the bottom and anoff-gas duct 33 departing from said interior space at the top. Lowermostzone 34 is separated from middle zone 35 by distributor bottom 37, whichevenly distributes over the entire cross-section of fluidized-bedreactor 30 the reducing gas flowing from bottom to top through interiorspace 31 of fluidized-bed reactor 30 and thereby produces a uniformfluidized bed of fine ore particles. The boundary between middle zone35, formed by the fluidized bed, and uppermost zone 36, which is calledfreeboard, is less pronounced than in the case of the two lower zones.In the freeboard, the gas space is calmed down, whereby the dischargingof ore particles from fluidized-bed reactor 30 is minimized. Inlowermost zone 34 below distributor bottom 37, a burner 38 is arranged,to which there lead an oxygen and/or air duct that is not represented aswell as a duct for reducing gas, export gas, cooling gas, externalcombustible gas and/or solid and/or liquid fuels. However, it is alsopossible that only one duct for oxygen and/or air is provided, with thecombustion of the reducing gas taking place directly in the reactor. Thehot combustion gases supply heat to the reducing gas flowing intofluidized-bed reactor 30 and/or lead to autoreforming reactions.Advantageously, materials increasing the proportion of reductants in thereducing gas, such as natural gas and/or coal, may also be admixed tothe reducing gas via burner 38.

[0042] In the embodiment represented in FIG. 7, burner 38 is arranged inmiddle zone 35, in the fluidized bed. This embodiment is advantageousparticularly when the reducing gas is very dust-loaded, given that thenthere is no risk that distributor bottom 37 is blocked by fusing dust.

[0043]FIG. 8 shows a preferred embodiment in which burner 38 is arrangedabove fluidized-bed 35, i.e. in freeboard 36. Here, the heat transfer isdone by radiation and/or convection by particles discharged from thefluidized bed.

[0044] The process variant illustrated in FIG. 9 exhibits substantiallyall of the features of the plant represented in FIG. 2. In contrast withFIG. 2, however, no export gas is fed via duct 26 and compressor 27 toburners 25, 25′ and 25″, provided in reducing-gas ducts 13 andreducing-gas feed duct 12, but external combustible gas and/or solidand/or liquid fuel which is transported to burners 25, 25′ and 25″ via aduct 39.

[0045] The invention is not limited to the exemplary embodimentsrepresented in the drawings but may be modified in various aspects. Forexample, it is possible to select the number of fluidized-bed reactorsaccording to requirements. Also, the reducing gas can be produced inaccordance with various known methods.

1. A process for the gas reduction of particulate oxide-containing ores,in particular iron-oxide-containing material, in the fluidized-bedprocess at a pressure of <5 bars, wherein the ore by aid of a reducinggas produced from coal is heated, optionally also pre-reduced, in afluidized-bed reactor (1) designed as a pre-heating stage (5),subsequently is reduced to sponge iron in at least one fluidized-bedreactor (2, 3) designed as a reduction stage (7, 8), the reducing gasvia a reducing-gas feed duct (12) or reducing-gas duct (13) beingconducted from the reduction stage (7, 8) to the pre-heating stage (5)in the opposite direction of the material to be reduced and conductedfrom stage to stage, and being drawn off as an export gas afterpurification, characterized in that heat is supplied to the reducing gasfed to the reduction stage (7, 8) and/or pre-heating stage (5), namelyby combustion, together with oxygen and/or air, of a portion of thereducing gas provided for the gas reduction in the reduction stage (7,8) and/or the pre-heating stage (5). (FIG. 1)
 2. A process for the gasreduction of particulate oxide-containing ores, in particulariron-oxide-containing material, in the fluidized-bed process at apressure of <5 bars, wherein the ore by aid of a reducing gas producedfrom coal is heated, optionally also pre-reduced, in a fluidized-bedreactor (1) designed as a pre-heating stage (5), subsequently is reducedto sponge iron in at least one fluidized-bed reactor (2, 3) designed asa reduction stage (7, 8), the reducing gas via a reducing-gas feed duct(12) or reducing-gas duct (13) being conducted from the reduction stage(7, 8) to the pre-heating stage (5) in the opposite direction of thematerial to be reduced and conducted from stage to stage, and beingdrawn off as an export gas after purification, characterized in thatheat is supplied to the reducing gas fed to the reduction stage (7, 8)and/or pre-heating stage (5), namely by combustion, together with oxygenand/or air, of a portion of the export gas. (FIGS. 2, 4)
 3. A processfor the gas reduction of particulate oxide-containing ores, inparticular iron-oxide-containing material, in the fluidized-bed processat a pressure of <5 bars, wherein the ore by aid of a reducing gasproduced from coal is heated, optionally also pre-reduced, in afluidized-bed reactor (1) designed as a pre-heating stage (5),subsequently is reduced to sponge iron in at least one fluidized-bedreactor (2, 3) designed as a reduction stage (7, 8), the reducing gasvia a reducing-gas feed duct (12) or reducing-gas duct (13) beingconducted from the reduction stage (7, 8) to the pre-heating stage (5)in the opposite direction of the material to be reduced and conductedfrom stage to stage, and being drawn off as an export gas afterpurification, characterized in that heat is supplied to the reducing gasfed to the reduction stage (7, 8) and/or pre-heating stage (5), namelyby combustion, together with oxygen and/or air, of a portion of thecooling gas used for cooling the reducing gas to be introduced into thefinal reduction zone (8). (FIGS. 3, 5)
 4. A process according to anyoneof claims 1 to 3, characterized in that the portion to be burnt of thereducing gas, export gas or cooling gas is subjected to a scrubbingoperation before being burnt.
 5. A process for the gas reduction ofparticulate oxide-containing ores, in particular iron-oxide-containingmaterial, in the fluidized-bed process at a pressure of <5 bars, whereinthe ore by aid of a reducing gas produced from coal is heated,optionally also pre-reduced, in a fluidized-bed reactor (1) designed asa pre-heating stage (5), subsequently is reduced to sponge iron in atleast one fluidized-bed reactor (2, 3) designed as a reduction stage (7,8), the reducing gas via a reducing-gas feed duct (12) or reducing-gasduct (13) being conducted from the reduction stage (7, 8) to thepre-heating stage (5) in the opposite direction of the material to bereduced and conducted from stage to stage, and being drawn off as anexport gas after purification, characterized in that heat is supplied tothe reducing gas fed to the reduction stage (7, 8) and/or pre-heatingstage (5), namely by combustion, together with oxygen and/or air, ofexternal combustible gas and/or solid and/or liquid fuel. (FIG. 9)
 6. Aprocess according to anyone of claims 1 to 5, characterized in that thecombustion is done in a burner (25) provided in the reducing-gas feedduct (12) or reducing-gas duct (13). (FIGS. 1, 2, 3, 9)
 7. A processaccording to anyone of claims 1 to 6, characterized in that thecombustion is done in a combustion chamber separated from thereducing-gas feed duct (12) or reducing-gas duct (13), the combustiongases and possibly not burnt solids subsequently being introduced intothe reducing-gas feed duct (12) or reducing-gas duct (13). (FIGS. 4, 5)8. A process according to anyone of claims 1 to 7, characterized in thatthe combustion is done by means of at least one burner (38) associatedwith the fluidized-bed reactor (30), the combustion gases beingintroduced directly into the fluidized-bed reactor (30). (FIGS. 6 to 8)9. A process according to claim 1, characterized in that oxygen and/orair are fed into the reducing-gas feed duct (12) or reducing-gas duct(13) via lances.
 10. A process according to claim 1, characterized inthat oxygen and/or air are fed into the fluidized-bed reactor (30) via aburner (38), preferably a lance.
 11. A process according to anyone ofclaims 1 to 10, characterized in that reducing gas and/or export gasand/or cooling gas and/or external combustible gas and/or solid and/orliquid and/or gaseous fuel on a hydrocarbon basis are further used forthe combustion, in addition to the gas respectively used.
 12. A processaccording to anyone of claims 1 to 11, characterized in that a materialincreasing the proportion of reductants in the reducing gas by at leastpartially reacting with the reducing gas, in particular natural gasand/or coal, is admixed to the reducing gas fed to the reduction stage(7, 8) and/or pre-heating stage (5).
 13. A process for the gas reductionof particulate oxide-containing ores, in particulariron-oxide-containing material, in the fluidized-bed process at apressure of <5 bars, wherein the ore by aid of a reducing gas producedfrom coal is heated, optionally also pre-reduced, in a fluidized-bedreactor (1) designed as a pre-heating stage (5), subsequently is reducedto sponge iron in at least one fluidized-bed reactor (2, 3) designed asa reduction stage (7, 8), the reducing gas via a reducing-gas feed duct(12) or reducing-gas duct (13) being conducted from the reduction stage(7, 8) to the pre-heating stage (5) in the opposite direction of thematerial to be reduced and conducted from stage to stage, and beingdrawn off as an export gas after purification, characterized in that amaterial increasing the proportion of reductants in the reducing gas byat least partially reacting with the reducing gas, in particular naturalgas and/or coal, is admixed to the reducing gas fed to the reductionstage (7, 8) and/or pre-heating stage (5).
 14. A plant for carrying outthe process according to anyone of claims 1 to 13, comprising at leasttwo fluidized-bed reactors subsequently connected in series for the gasreduction of particulate oxide-containing ores by means of a CO andH₂-containing reducing gas produced from coal, comprising a reducing-gasfeed duct (12) leading to the fluidized-bed reactor (3) arranged lastwhen seen in the direction of flow of the oxide-containing material, adischarge duct (14) departing from the fluidized-bed reactor (1)arranged first when seen in the direction of flow of theoxide-containing material and discharging spent reducing gas as exportgas, a gas recycle duct (22) for cooling gas, branching off thereducing-gas feed duct (12) and running back into the reducing-gas feedduct (12) via a scrubber (23), and comprising a reducing-gas duct (13)provided for conducting the reducing gas from one fluidized-bed reactor(3) into the preceding fluidized-bed reactor (1, 2), characterized inthat the plant is flow-connected with at least one burner (25, 38)having a feed duct (12, 13, 26, 28, 39) for reducing gas and/or exportgas and/or cooling gas and/or external combustible gas and/or solidand/or liquid fuel and/or oxygen and/or air for the combustion of aportion of the reducing gas, export gas or cooling gas, of externalcombustible gas or solid or liquid fuel together with oxygen and/or air.15. A plant according to claim 14, characterized in that a scrubber (15)is provided in the export-gas discharge duct (14) and scrubbed exportgas is feedable to the burner (25) via an export-gas duct (26). (FIGS.2, 4)
 16. A plant according to claim 14 or 15, characterized in that theburner (25) with its combustion chamber (25 a) is provided directly inthe reducing-gas feed duct (12) or the reducing-gas duct (13). (FIGS. 1to 3, 9)
 17. A plant according to anyone of claims 14 to 16,characterized in that the burner (25, 38) is designed as an oxygenand/or air lance.
 18. A plant according to anyone of claims 13 to 16,characterized in that the burner (25) has a combustion chamber (25 a)separated from the reducing-gas feed duct (12) or reducing-gas duct(13), which is flow-connected with the reducing-gas feed duct (12) orreducing-gas duct (13). (FIGS. 4, 5)
 19. A plant according to anyone ofclaims 13 to 17, characterized in that the burner (38) is arranged in afluidized-bed reactor (30), namely either below the fluidized bed (35),on the level of the fluidized bed (35) or above the fluidized bed (35).(FIGS. 6 to 8)